"He's going to have a lot of sacks late in the down," left tackle Donald Penn said of the 2014 draft's No. 5 overall pick, per CSN Bay Area. "He has a motor that's relentless. As a tackle, you have to stay on him until you hear the whistle or hear the crowd cheer."

The 29th annual Butkus Award finalist out of Buffalo brings freakish combine numbers and ferocious athleticism off the edge to a defense in need of youth. Mack told Around The League at last month's NFLPA Rookie Premiere that nobody has been a bigger help to his development than veteran end Justin Tuck.

"I see signs," Penn said of Mack. "In between snaps, he's in Justin Tuck's ear. Khalil's a special athlete. I can tell from some of his moves and the way he can put his foot in the ground and change directions, for him to be doing that at defensive end, he moves like a defensive back. It's crazy for a guy that size to be doing that."

Nobody can accuse Reggie McKenzie of passivity. Oakland's general manager has revamped last year's 22nd-ranked squad into a veteran-heavy unit with a bright young centerpiece in Mack. Dennis Allen is under considerable pressure to put it all together come September.